15 research outputs found
Laser-induced bound-state phases in high-order harmonic generation
We present single-molecule and macroscopic calculations showing that
laser-induced Stark shifts contribute significantly to the phase of high-order
harmonics from polar molecules. This is important for orbital tomography, where
phases of field-free dipole matrix elements are needed in order to reconstruct
molecular orbitals. We derive an analytical expression that allows the
first-order Stark phase to be subtracted from experimental measurements
Two-center minima in harmonic spectra from aligned polar molecules
We extend a model of two-center interference to include the superposition of
opposite orientations in aligned polar molecules. We show that the position of
the minimum in the harmonic spectrum from both aligned and oriented CO depends
strongly on the relative recombination strength at different atoms, not just
the relative phase. We reinterpret the minimum in aligned CO as an interference
between opposite orientations, and obtain good agreement with numerical
calculations. Inclusion of the first-order Stark effect shifts the position of
the interference minimum in aligned CO even though aligned molecules do not
posses total permanent dipoles. We explain the shift in terms of an extra phase
that the continuum electron of oriented CO accumulates due to the Stark effect
Vold i massemedierne En socialkonstruktivistisk analyse af massemediernes voldsfremstillinger
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Endocarditis in Greenland with special reference to endocarditis caused by Streptococcus pneumoniae
Multiphoton quantum dynamics of many-electron atomic and molecular systems in intense laser fields
Attosecond transient absorption spectroscopy of molecular nitrogen: Vibrational coherences in the b′ 1Σ+u state
Nuclear and electronic dynamics in a wavepacket comprising bound Rydberg and valence electronic states of nitrogen from 12 to 15 eV are investigated using attosecond transient absorption. Vibrational quantum beats with a fundamental period of 50 femtoseconds persist for a picosecond in the b′ 1Σ+u valence state. Multi-state calculations show that these coherences result primarily from near infrared-induced coupling between the inner and outer regions of the b′ 1Σ+u state potential and the dark a″ 1Σ+g state. The excellent spectral and temporal resolution of this technique allows measurement of the anharmonicity of the b′ 1Σ+u potential directly from the observed quantum beats